Apparatus for operating electric discharge lamps including an impedance simulator



y 6, 1965 w. F. POWELL, JR 3,193,726

APPARATUS FOR OPERATING ELECTRIC DISCHARGE LAMPS INCLUDING AN IMPEDANCE SIMULATOR Filed Aug. 27, 1962 2 Sheets-Sheet 1 BY W ATTORNEY July 6, 1965 w F. POWELL, JR 3,193,726

APPARATUS FOR OPERATING ELECTRIC DISCHARGE LAMPS INCLUDING AN IMPEDANCE SIMULATOR 2 Sheets-Sheet 2 Filed Aug. 27, 1962 2 LQQbQQ AAAAA I NVENTOR. Wa/ 25291" FP0We/4 J2? w a W ATTOR NEY APPARATUS FOR OPERATING ELECTRIC DE- CHARGE LAMPZS INCLUDENG Ah I FED SIMULATUR I M ANKZE Walter F. Powell, .l'r., Danville, IlL, assignor to General Electric Company, a corporation of New York Filed Aug. 27, 1962, er. N 219,452 10 Claims. (Q1. 315-199) TlllS invention relates generally to apparatus for operatfig electric dlisclharge devices such as fluorescent lam s.

ore par icu ar it relates to a r L operating such devices. n Improved appaatus fox The principal functions of a ballast are to provide the requisite operating and starting voltages for the electric discharge device and to regulate the lamp current. Passive type of ballasts have been generally used in the past to start and operate electric discharge devices such as fluorescent lamps or mercury vapor lamps. In such passive type of ballasts, a reactive element is usually em ployed to provide the current regulating action required because of the negative resistance characteristic of the electric discharge device. The reactive element used may be a s mple inductor or a high leakage reactance secondary winding of a ballast transformer Where volta e transformations are necessary to start or operate the electric discharge device.

In a commonly used arrangement, the reactive element the electric discharge device and a driving voltage source are operatively associated in a series loop arrangement.

When the current through the electric discharge device tends to increase above its normal eratin voltage drop P g el, the

across the reactive element increases. This causes thevoltage across the electric discharge device to decrease since the sum of the voltage drop in the series c1rcu1t must be equal to the driving voltage. Conversely when the lamp current decreases below its normal operat mg level, the voltage drop across the reactive element decreases thereby causing the voltage across the lamp to increase. In this manner, the energy supplied to the electric discharge device is effectively regulated.

An inherent disadvantage of conventional passive ballasting systems is that the peak energy stored in the react1ve element must be maintained at a relatively high level to carry out the ballasting function. Also, in order to prov1de satisfactory regulation for supply voltage variations between plus or minus ten percent of the rated voltage, it is required that the passive ballasting voltampere characteristic intersect the normal volt-ampere characteristic of the electric discharge lamp at a relatlvely steep angle. This imposes severe requirements on the volt-ampere ratings of the reactive elements used in the pass1ve type of ballasts and results in heavy bulky react1ve devices. There is a need, therefore, for a ballast apparatus wherein the volt-ampere requirements can be 1rareldrced while achieving satisfactory regulation and sta- In a conventional 60 cycle ballast for operating one rapid start type of lamp, it is generally required that the supply voltage be about 100 to 200 percent greater than the operating voltage. This relatively large difference in the lamp operating voltage and the supply voltage is required to achieve satisfactory regulation. It is desirable that the necessity for providing a substantial difference between lamp operating voltage and the supply voltage be eliminated.

In general, it is an object of the invention to provide an unproved apparatus for operating one or more electric discharge lamps.

A more specific object of the invention is to provide an improved apparatus for operating electric discharge lamps wherein the volt-amperes required to achieve satisfactory 3,193,726 Patented July 6, 1965 ice regulation are significantly reduced as compared with the volt-amperes required in a comparable passive ballast.

It is another object of the invention to provide an improved apparatus for operating electric discharge lamps, such as fluorescent lamps, that does not require a substantial difference between the open circuit voltage and the operating voltage of the electric discharge lamp to achieve satisfactory regulation of the lamp current.

In accordance with one form of my invention, I have provided an improved apparatus for operating one or more electric discharge lamps in which a. phase shifting means is utilized in conjunction with a signal amplifying means to provide a voltage in the lamp circuit to control the operation of the lamp or lamps. This voltage has a predetermined phase relationship with the lamp current. The phase shifting means is connected in circuit with one of the output leads and is adapted to receive a feedback signal as some function of the current supplied by the apparatus at the input lead. This signal is converted to a phase shifted signal having a predetermined phase relationship with respect to the feedback signal. The output of the phase shifting means is coupled with the signal amplifying means to provide a voltage in the lamp circuit that has the same predetermined phase relationship with respect to the lamp current as the phase-shifted signal, and that varies functionally with the phase-shifted signal to control the operation of the lamp or lamps.

According to another aspect of my invention, a differentiating circuit is employed as the phase shifting means where it is desired to control the operation of the lamp or lamps by an output voltage that simulates the voltage across the series inductor. The differentiating circuit causes the phase-shifted signal to lead the lamp current by ninety degrees thereby causing the output voltage of the voltage amplifying means to lead the lamp current by ninety degrees.

Where one or more electric discharge lamps are to be operated in a lead circuit arrangement, an integrating circuit may be employed as the phase shifting means to drive the signal amplifying means with a signal that is a function to the time integral of the lamp current. Thus, the signal amplifying means will provide a voltage that simulates the voltage across a series capacitor connected in the lamp circuit. Preferably, a push pull amplifier energized from a direct current source may be employed as a signal amplifying means.

The subject matter which I regard as my invention is particularly pointed out and claimed in the concluding portion of this specification. My invention, however, both to structure and manner of operation together with further objects and advantages thereof may be best understood by reference to the following description taken in conjunction with the accompanying drawings:

FIGURE 1 is a schematic illustration of one embodiment of the invention wherein a voltage is provided in the lamp circuit simulating the voltage across a series capacitor;

FIGURE 2 is a schematic circuit diagram of the operational amplifier shown in block form in FIG. 1;

FIGURE 3 is a schematic illustration of another form of my invention wherein the voltage across a series inductor is simulated to provide the ballasting action in the lamp circuit; and

FIGURE 4 is a schematic circuit diagram of another embodiment of my invention wherein the control voltage introduced in the lamp circuit has a predetermined phase relationship with the lamp current.

Referring now more specifically to FIGURES 1 and 2, I have shown therein an apparatus generally identified by reference numeral 10 for operating a fluorescent lamp L. The apparatus It is shown enclosed in a dashed rectangle which schematically represents an enclosure 11 for the apparatus 10. A pair of input terminal leads 12, 113 are provided for connection to a suitable alternating current source. The output of the apparatus Jill is applied across the fluorescent lamp L by means of output leads l4 and 15. Fluorescent lamp L is disposed in proximity to a grounded conductive plate or fixture to so that it is disposed in capacitive relationship with the conductive plate 16 to facilitate starting of the fluorescent lamp 'L.

To control the operation of the fluorescent lamp L, I have provided a power stage which includes a pair of transistors Q and Q a direct current source 17, an output transformer T and a coupling transformer T The transistors Q and Q are driven by voltages induced across the secondary windings S S which are induc tively coupled on a magnetic core 18. The primary Winding P is coupled with an integrating circuit comprised of an operational amplifier A, a capacitor C and resistors R, R Resistor R provides the DC. bias for the operational amplifier A. The resistor R and capacitor C serve as the integrating elements.

it will be seen in FIGURE 1 that the secondary winding S of the output transformer T is connected in circuit with input lead 13. In this form of my invention, the voltage across the secondary winding S leads the lamp current and simulates the voltage across a series capacitor. Further, it will be seen that primary windings P P are inductively coupled with the secondary winding S on a magnetic core 19 and are connected in circuit with the transistors Q Q and the DC. power source 17. A resistor R is connected across the secondary winding It will be understood that transformer T must have a low magnetizing re'actance or high magnetizing current. If the transformer'T does not, as was the case in the exemplification of the invention, the resistor R was added to lowor the impedance that the transformer T places in the lamp circuit.

As will be seen in FlGURE 1, primary winding P is connected in circuit across the emitter and collector electrodes of transistor Q and in circuit with the negative side of the direct current power source 17 by means of leads Ztl, 21, 21b. Similarly, primary winding P is connected by leads 21, 21b, 22 in circuit across the emitter and collector electrodes of transistor Q and in circuit with the negative side of the direct current source. Resistors R R R control the biasing conditions of transistor Q while resistors R R R control the biasing conditions of transistor Q It will be noted that the emitter to base voltage of the PNP transistors Q and Q is controlled by transformer T which has a pair of symmetrical secondary windings S and S coupled across the emitter and base electrodes of transistors Q Q When voltage induced across second ary winding S has a polarity such that the upper end of the secondary winding 3 as viewed in FIGURE 1, is more negative than its lower end, transistor Q will be forward biased. A current will flow through the base and emitter electrodes of the transistor Q and this current fiow will cause the emitter-to-collector impedance to be reduced. Accordingly, a current will flow from the positive terminal of the D.C. power source through lead Me, the emitter and collector electrodes of transistor Q lead 29, primary winding P and lead 21. in the next alternation transistor Q and primary winding P come into play.

The power amplifier is driven by the output signal of an integrating circuit which includes the operational amplifier A, the capacitor C and the resistors R, R and R A capacitor C is connected with output of the operational the exemplification of my invention to be hereinafter more fully described. The operational amplifier A is energized from a DC. source 7.6 and is comprised of a pair of compound-connected transistor Q Q In such an arrangement, the common emitter current gain is approximately equal to the product of the individual current gains of transistors Q and Q When the input signal supplied at input lead 24 of the operational amplifier A is positive going, the positive going signal adds to the forward bias thereby causing an increase in the base current. As the base current increases, the collector current increases, and the voltage drop across the resistor R increases in magnitude. The polarity of this voltage drop is such that the bias current to the base of transistor Q is reduced. Hence, the increased current at the input of amplifier A is opposed by a feedback from the amplifier output through the capacitor. C and resistor R. The operational amplifier A tends to maintain the input of the amplifier A virtually at the quiescent bias current condition.

The integrating circuit provides an A.C. signal at the output of the amplifier A that is proportional to the time integral of the AC. signal applied at its input. In other words, the signal applied across the primary winding P to drive the power amplifier circuit will lag the signal applied at the amplifier input by ninety degrees. Thus, the integrating circuit functions as a phase shifting means to shift the phase of the feedback signal.

Referring to both FIGURES 1 and 2, the operation of the apparatus ll will now be more fully explained. Operation of the apparatus 1% is initiated by connecting the input terminal leads l2, 13 in circuit with a suitable power source. During the open circuit condition, the source voltage will be initially applied across output leads 14, 15 and the fluorescent lamp L will ionize and conduct cur rent. When lamp L conducts current, a current will then flow through the resistor R and a feedback signal proportional in magnitude to the lamp current will be supplied at the input lead 24- of the operational amplifier A.

Let us take an arbitrary alternation of the power source when the polarity of the voltage supplied is such that input terminal lead 12 is positive with respect to input terminal lead 13. The path of the current fiow will be essentially from the input terminal lead 12 to output lead 14, lamp L, output lead 15, resistor R the secondary winding S to input terminal lead 13. The polarity of the voltage drop across the resistor R will be such that its right end as viewed in FIGURE 1 is positive with respect to its left end. Thus, the input signal supplied at the input lead 24 of the operational amplifier A is also positive.

it will be appreciated that at the start of the positive tall cycle the voltage and current at the input of the operational amplifier A will tend to increase in a positive direction. However, this tendency of the voltage at the input of amplifier A to increase is opposed by the feedback current from the amplifier output through the parallel combination of capacitor C and resistor R. As the voltage increases in the positive halt cycle, the charging current to capacitor C must also proportionally increase so that the current at the input of the amplifier A is substantially maintained at theinitial level. In order that this charging current be supplied to capacitor C the output voltage of the amplifier A varies so that it will be proportional to the integral of the charging current. Accordingly, the output signal will be proportional to the negative integral of the signal applied at the input of amplifier A. This output signal is applied across the primarywinding P of transformer T to drive the transistors Q and Q and thereby provide an amplified output voltage that is proportional to the time integral of the lamp current.

During the negative alternation of the power supply; the phase angle of the signal applied across the primary winding P of the transformer T will also be displaced ninety degrees with respect to the phase angle of the lamp current, since it will be proportional to the time integral of the lamp current or the current supplied at output leads 14, 15. In both alternations of the power supply, the output signal of the integrating circuit is used to drive the transistors Q Q in a push pull parallel arrangement to provide an amplified voltage across the secondary winding S that is proportional to the time integral of the lamp current. Thus, during each half cycle of the power supply regulation of the current supplied to the lamp L is achieved by providing a voltage that simulates the voltage developed across a series capacitor.

It will be appreciated that the voltage across a capacitor in series with the power source lags the current by ninety degrees or a quarter cycle. If we assume that the current is essentially sinusoidal in waveshape, the voltage across the series capacitor will have a waveshape in the form of a negative cosine.

Accordingly, it will be apparent that the apparatus produces a control voltage that simulates the voltage across a series capacitor to regulate the lamp current. Since this voltage is controlled in response to a phaseshifted signal from the lamp circuit, it is possible to achieve current regulation with a smaller difference between the open circuit voltage and the lamp operating voltage than would be the case if a capacitor were used for the purpose of regulation. It will be appreciated that in order to achieve satisfactory current regulation and stability in a conventional ballast, the supply voltage must be about 100 percent greater than the operating voltage required for the fluorescent lamp.

For the convenience of those desiring to practice the present invention, the following specific circuit components used in the exemplification of the invention shown in FIGURES 1 and 2 are given by way of illustration:

Resistor R 100,000 ohms, 1 watt. Resistor R 230 ohms, 450 watts. Resistors R R 470,000 ohms, 1 watt. Resistors R R 220 ohms, 1 watt. Resistors R R a. 100 ohms, /2 watt. Resistor R 10 ohms, 2 watts. Resistor R 2,700 ohms, 1 Watt. Resistor R 1,000 ohms, watt. Resistor R 100 ohms, 2 watts. Transistors Q Q 2N1542. Transistors Q Q 2N30l. Zener diodes Z Z IN3044B, 100 volt, 1 watt. Capacitor C 0.4 microfarad. Capacitor C 100 microfarads. Transformer T General Electric 9T51Y6232, .5 lrva. Transformer T General Electric 9T51Y6428, .1 kva. Fluorescent lamp L FlSWTlZ rapid start.

The apparatus 10 constructed with the foregoing components operated the fluorescent lamp L with a power factor of approximately .897 at a lamp voltage of 43 volts R.M.S. The input leads 12, 13 were connected with a 70 volt, 60 cycle A.C. source. A D.C. source 17 of 50 volts was used to energize the power amplifier circuit and a D.C. source of 20 volts was used to energize the amplifier A. The feedback voltage was approximately 37 volts R.M.S. and the lamp current was measured at .300 ampere.

Referring now to FIGURE 3, I have illustrated therein an apparatus 30 substantially similar to the apparatus shown in FIGURE 1 wherein a differentiating circuit is employed instead of an integrating circuit as a phase shifting means. For the purpose of simplification, I have identified the corresponding parts shown in FIGURES 1 and 3 with the same reference numerals. It will be seen in FIGURE 3 that the operational amplifier A in conjunction with the feedback resistor R and capacitor C functions as a differentiating circuit. Thus, the feedback signal supplied at the input lead of the operational amplifier A is converted to a phase-shifted signal at output lead 23 that is proportional to the negative first derivative with respect to time of the input signal. The transistors Q and Q of apparatus 30 are driven by the phase-shifted signal and are operated in a push pull parallel arrangement to provide a voltage across the secondary winding S that leads the lamp current. Thus, the voltage across the secondary winding S simulates the counter electromotive force of a series inductor.

Regulation of the current flowing through the lamp L is achieved in a way similar to a circuit utilizing a series inductor in the lamp circuit. As the current through the lamp L tends to increase the signal supplied at the feedback transformer T is also increased in magnitude thereby causing the voltage induced across the secondary Winding S to be increased. Since the voltage across the secondary winding S has a vector opposing relation with the supply voltage, the voltage applied across the lamp is decreased. When the current through the lamp L tends to decrease, the power amplifier stage driven by the transformer T causes the voltage across the secondary winding S to decrease thereby increasing the potential across the lamp L and causing the current to return to its normal operating level.

A ballast apparatus 30 was constructed and successfully operated an FISWTlZ rapid start fluorescent lamp. Essentially, the same components were used in the circuit shown in FIGURES 1 and 2 except that the capacitor C was eliminated and the capacitor C was substituted for the resistor R to convert the integrating circuit to a differentiating circuit.

In Table I, I have set forth the data obtained for ballast apparatus 30 employing substantially the same components as were used in apparatus '10 except as noted above. The value of the capacitance of the capacitor C in series with the input of the operational amplifier A was varied to control the feedback gain.

Table I It was found that for different values of the capacitance of the capacitor C the phase in the feedback circuit did not shift. The input leads 12, 13 were connected across a 70 volt, 60 cycle source and a 50 volt D.C. source was used to energize the push pull amplifier.

Referring now to FIGURE 4, I have illustrated therein an apparatus 40 incorporating another form of my invention in which a variable resistor R and a capacitor C are utilized as a phase shifting means to provide a signal at the input of the power stage to provide a phase-shifted control voltage. Depending upon the particular setting of the variable resistor R the signal across leads 41, 42 has a predetermined phase displacement with respect to the voltage across resistors R R Input leads 43, 44 are provided for connection to an alternating power source. Output leads 45, 4e are connected in circuit with a fluorescent lamp L to apply the output voltage across lamp L. The lamp L is disposed in proximity to a grounded conductive plate or fixture 47 to facilitate startmg.

As in the other illustrated embodiments of my invention, I have also employed a push pull amplifier stage employing a pair of PNP transistors Q and Q in a common emitter connection to amplify the signal supplied at input leads 41, 42. A pair of voltage dropping resistors R R are provided at the input of the parallel inverter power stage. When the upper end of the serially connected resistors R R is more negative with respect to the lower end, transistor Q will be forward biased and when the lower end is more negative than the upper end, transistor Q, will be forward biased. The resistors R R and R R and R control the biasing conditions for transistors Q and Q respectively. A DC. power source 43, represented schematically by a battery, provides the power for the parallel inverter circuit. Zener diodes Z Z protect the transistors Q Q against transient voltages that might damage the transistors.

The output of the power amplifier circuit is stepped-up by a control transformer T The control transformer T has a center tapped primary winding comprised of the primary portions P P which are inductively coupled with a secondary winding 5.; on a magnetic core 49. Since the transformer T had a low magnetizing reactance, a resistor R was provided to lower the impedance that the transformer T places in series with the lamp L.

During operation, lamp current will flow through the resistors R and R and thereby cause a feedback signal to fiow through the phase shifting network comprised of the variable resistor R and the capacitor C A signal which is phase displaced with respect to the lamp current is coupled with the input of the power amplifier circuit and drives the stage so that an increased voltage having the phase displacement of the input signal is provided at the output. The voltage across the secondary winding 5.; is in opposing relationship vectorially with the voltage impressed across the input terminal leads 43, 44.

Regulation of the lamp current is achieved in the same manner as in the other circuits shown in FIGURES l and 3. When the lamp current tends to increase in magnitude, the phase displaced voltage across the secondary winding S; also increases in magnitude to provide a decreased voltage across the lamp L. Vice versa, when the lamp current tends to decrease, the voltage induced across the secondary winding S also decreases in magnitude thereby causing the lamp voltage to increase.

By way of a specific exemplification, the apparatus 40 was constructed to operate a 15 watt rapid start lamp. A small filament transformer (not shown) in the simplified schematic circuit diagram of FIGURE 4 was used to provide a continuous supply of cathode heating current since the lamp L'operated by the apparatus 40 was of the hot cathode type. The apparatus 40 may employ the following circuit components which are cited by way of illustration:

In Table 11 below, I have set forth the data obtained for five different settings of the variable resistor R Table 11 Setting of the variable resistor B10 in ohms 10,000 470 220 100 47 Phase shift in current relative to liu voltage, degrees 27 32. 2 31. 8 37. 39. 8 Power factor .890 .840 .850 .800 .768 Lamp voltage (RM. 44.7 45.0 45.0 45.4 44.5 Control voltage (RM. output power amplifier 20 16.0 13 3 9. 8. 0

'An advantage of the apparatus 40 shown in FIGURE 4 as compared with the other circuits is that the use of a computer element such as the operational amplifier is not required.

From the foregoing description of the apparatus of the invention and its operation, it will be apparent that because of the adaptability of the circuit-s to feedback control satisfactory current regulation can be achieved without need for capacitors or reactive elements having relatively high volt-ampere requirements. Although filament transformer have not been shown in the illustrated schematic diagrams, it will be understood that where hot cathode type of electric discharge lamps are operated a constant supply of heating current must be supplied to the lamps. Further, it will be understood that various auxiliary starting aid circuits other than those shown may be employed in conjunction with the apparatus of the invention to aid in starting of the lamp or lamps operated by the apparatus.

It will be apparent from the above description of the various specific exemplifications of my invention that many modifications may be made by those skilled in the art without actually departing from the invention. a It is, therefore, intended in the appended claims to cover all such equivalent variations that come within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

l. An apparatus for operating an electric discharge lamp from a power source comprising: at least one electric discharge lamp, circuit means for connecting a power source and the electric discharge lamp in a lamp operating circuit and including output leads for supplying the output of the apparatus to the electric discharge lamp, a phase shifting means having an input adapted to receive a feedback signal and an output providing an output signal having a predetermined phase relationship with respect to said feedback signal, circuit means coupling the input of said phase shifting means in circuit with one of said output leads to provide at the input of said phase shifting means a feedback signal functionally related to the current supplied to the electric discharge lamp, an amplifying means for producing in the lamp operating circuit a voltage having substantially the same predetermined phase relationship with respect to the feedback signal as the outsignal, said amplifying means having its input coupled with the output of said phase shifting means and having its output connetced in circuit with an input lead.

2. An apparatus for operating at least one fluorescent lamp from a power source comprising: circuit means for connecting the power source in circuit with at least one fluorescent lamp and including input leads from connection with the power source and output leads for connection with said at least one fluorescent lamp to supply the output of the apparatus to the lamp, a phase shifting means having an input for receiving a feedback signal and an output providing an output signal having a predetermined phase relationship with respect to said feedback signal, circuit means coupling the input of said phase shifting means in circuit with one of said output leads to provide at the input of said phase shifting means a feedback signal functionally related to the current supplied at said output leads, a signal amplifying means having its output coupled with the output of said phase shifting means and providing at its output a voltage that has essentially the same predetermined phase relation with respect to the current supplied at the output leads as the output signal and that proportionally varies with the output signal of said phase shifting means, said output of said signal amplifying means being coupled with one of said input leads whereby the voltage at said output is vectorially added to the voltage applied across the input leads, said voltage at the output of said signal amplifying means being controlled in response to said feedback signal to provide the ballasting action required for operation of at least one fluorescent lamp.

3. An apparatus for operating at least one fluorescent lamp from a voltage source, said apparatus comprising: at least one fluorescent lamp, circuit means for connecting a voltage source and said at least one fluorescent lamp in a lamp operating circuit and including output leads for connection with the lamp to supply the output of the apparatus to said at least one lamp, a feedback means connected in the lamp operating circuit for providing a feedback signal functionally related to the current supplied to a fluorescent lamp, a phase shifting means coupled with said feedback means for converting said feedback signal to a phase shifted signal that is displaced ninety degrees in its phase relationship with respect to said feedback signal, a signal amplifying means having it output connected in the lamp operating circuit for providing a voltage in the lamp operating circuit that is substantially ninety degrees out of phase with said current and having its input coupled with the output of said phase shifting means, said voltage at the output of said signal amplifying means being controlled in response to said phase shifted signal to regulate the current supplied to the electric discharge lamp.

4. In an apparatus for operating at least one fluorescent lamp from an alternating voltage source, circuit means including an input for connection with the alternating voltage source and output leads for connection with at least one fluorescent lamp to supply the output of the apparatus thereto, a feedback means connected in circuit with at least one of said output leads to supply a feedback signal functionally related to the current in said output lead, a phase shifting means coupled with the said feedback means to provide a phase shifted signal having a predetermined phase relationship with said feedback signal, a power amplifier circuit for providing a voltage having essentially the same predetermined phase relationship with respect to said feedback signal as the phase shifted signal, said power amplifier circuit having its output connected in circuit with said input, said power amplifier circuit having its input coupled with the output of said phase shifting means and being driven in response to said phase shifted signal, said voltage at the output of said power amplifier circuit being in vectorial opposing relationship with the voltage of the source applied across the input.

5. In a ballast apparatus for operating at least one electric discharge lamp from an alternating power source, circuit means including input leads for connection with the alternating power source and output means connected with said at least one electric discharge lamp to supply the output of the apparatus thereto, a feedback means connected in circuit with said output means and providing a feedback signal indicative of the current supplied to t-he output means, a phase shifting means coupled with said feedback means and providing a phase shifted sign-a1 having a predetermined phase relationship with respect to said feedback signal such that said phase shifted signal is displaced from said feedback signal by approximately ninety degrees, amplifying means for providing a voltage at its output having the same predetermined phase relationship With respect to said feedback signal as said phase shifted signal, said amplifying means coupled with said feedback means and having its output connected in circuit with said at least one electric discharge lamp.

6. An apparatus for operating an electric discharge lamp from an alternating voltage source comprising: an alternating voltage source, at least one electric discharge lamp, circuit means connecting the voltage source and said at least one electric discharge lamp in a lamp operating circuit, a feedback means coupled in the lamp operating circuit for providing a feedback signal proportional to the magnitude of the current supplied to said at least one electric discharge lamp, a phase shifting means coupled with said feedback means, said phase shifting means converting said feedback signal to a phase shifted signal having a predetermined phase relationship with respect to said feedback signal, amplifying circuit means for providing in the lamp operating circuit a phase shifted voltage having the same predetermined phase relationship iii with respect to said feedback signal as said phase shifted signal, said amplifying circuit means including a pair of transistors coupled with said phase shifting means so that said transistors are driven in response to said phase shifted signal, said phase shifted voltage providing the ballasting action for the electric discharge lamp.

*7. In an apparatus for operating at least one electric discharge lamp, an alternating power source, circuit means connecting the alternating power source and the electric discharge lamp in a lamp operating circuit, a phase shifting means connected in the lamp operating circuit for providing a phase shifted signal proportional to the current supplied to the electric discharge lamp but having a predetermined phase relationship therewith, a signal amplifying means for providing in the lamp operating circuit a voltage having the same predetermined phase relationship with respect to the lamp current as said phase shifted signal, said signal amplifying means including an output transformer, said transformer including at least one primary winding energized by the output of said signal amplifying means and having a secondary Winding connected in circuit with said at least one electric discharge lamp to provide a voltage across said secondary Winding that is in vectorially opposing relation with the voltage of the alternating current source, said output of said signal amplifying means controlling the operation of said at least one electric discharge lamp in response to the said phase shifted signal.

S. The apparatus set forth in claim 7 wherein an impedance element is connected in shunt with said secondary winding of said transformer.

9. In an apparatus for operating at least one electric discharge lamp, a voltage source, circuit means for connecting the electric discharge lamp and voltage source in a lamp operating circuit, an integrating circuit coupled in the lamp operating circuit to provide a signal proportional to the time integral of the current supplied to the electric discharge lamp during operation, an amplifying means coupled with said integrating circuit, said amplifying means being driven in response to said signal and having its output connected in the lamp operating circuit to provide a voltage in generally opposing relationship to the voltage of the voltage source and proportional to the time integral of the current supplied at the output leads to control the operation of at least one electric discharge lamp.

lit). in an apparatus for operating at least one electric discharge lamp from a voltage source, circuit means for connecting at least one discharge lamp and the voltage source in a lamp operating circuit, a differentiating circuit having its input coupled with the lamp operating circuit to provide a signal at its output proportional to the current supplied to the electric discharge lamp during operation, a signal amplifying means coupled with the output of said dif erentiating circuit, said signal amplifying means having its output coupled With the lamp operating circuit to provide an output voltage in a generally opposing relationship With the voltage of the source during operation, said output voltage being controlled in response to said signal to simulate the voltage across a series inductor, thereby controlling the operation of said at least one discharge lamp.

References Cited by the Examiner UNITED STATES PATENTS 2,841,239 7/58 Hall et al. 55-105 2,990,509 6/61 Hauck 32366 X 3,130,347 4/64 Harpley 3l5--198 X 3,159,766 12/64 Harpley 315 GEORGE N. WESTBY, Primary Examiner. 

1. AN APPARATUS FOR OPERATING AN ELECTRIC DISCHARGE LAMP FROM A POWER SOURCE COMPRISING: AT LEAST ONE ELECTRIC DISCHARGE LAMP, CIRCUIT MEANS FOR CONNECTING A POWER SOURCE AND THE ELECTRIC DISCHARGE LAMP IN A LAMP OPERATING CIRCUIT AND INCLUDING OUTPUT LEADS FOR SUPPLYING THE OUTPUT OF THE APPARATUS TO THE ELECTRIC DISCHARGE LAMP, A PHASE SHIFTING MEANS HAVING AN INPUT ADAPTED TO RECEIVE A FEEDBACK SIGNAL AND AN OUTPUT PROVIDING AN OUTPUT SIGNAL HAVING A PREDETERMINED PHASE RELATIONSHIP WITH RESPECT TO SAID FEEDBACK SIGNAL, CIRCUIT MEANS COUPLING THE INPUT OF SAID PHASE SHIFTING MEANS IN CIRCUIT MEANS COUPLING THE INPUT OF PUT LEADS TO PROVIDE AT THE INPUT OF SAID PHASE SHIFTING MEANS A FEEDBACK SIGNAL FUNCTIONALLY RELATED TO THE CURRENT SUPPLIED TO THE ELECTRIC DISCHARGE LAMP, AN AMPLIFYING MEANS FOR PRODUCING IN THE LAMP OPERATING CIRCUIT A VOLTAGE HAVING SUBSTANTIALLY THE SAME PREDETERMINED PHASE RELATIONSHIP WITH RESPECT TO THE FEEDBACK SIGNAL AS THE OUTPUT SIGNAL, SAID AMPLIFYING MEANS HAVING ITS INPUT COUPLED WITH THE OUTPUT OF SAID PHASE SHIFTING MEANS AND HAVING ITS OUTPUT CONNECTED IN CIRCUIT WITH AN INPUT LEAD. 